This work focuses primarily upon radionuclide ventricular function techniques for evaluating cardiac performance under a variety of physiologic states. We have had the opportunity of evaluating and validating both the first-pass technique employing a computerized multicrystal camera as well as the multiple gated acquisition cardiac blood pool study. Both techniques have been standardized against contrast angiography and against each other. Furthermore, the intrinsic variability of ejection fraction measurements using either technique has been established. Studies have been performed sequentially following acute myocardial infarction. Furthermore, the utility of measurements obtained during exercise has been evaluated. These latter studies involve primarily the use of the first-pass radionuclide angiocardiogram. Both left and right ventricular performance during exercise has been characterized in patients with coronary artery disease both with and without acute myocardial infarction. The potential efficacy of these techniques for assessing interventions has been studies in a variety of protocols involving propranolol, aminophylline, and doxorubicin. Additional studies have involved evaluation of the use of radiolabeled cells, namely leukocytes and platelets, for imaging pathophysiologic processes involving cellular deposition.